Most posts you see on Facebook and other social media sites have a photo attached and there’s a good reason for it. Visual content grabs people’s attention and will make them stop, react, and possibly leave a comment on your post.
Instagram is all about photos. The more beautiful the settings and/or colors, the more people will stop to react to it, thus gaining even more attention for your profile and hopefully gaining more followers.
The more people who react and comment on your photos and posts, the more social proof you gain.